Evaluation and mechanism of ammonia nitrogen removal using sediments from a malodorous river

Malodorous rivers are among the major environmental problems of cities in developing countries. In addition to the unpleasant smell, the sediments of such rivers can act as a sink for pollutants. The excessive amount of ammonia nitrogen (NH₃-N) in rivers is the main factor that causes the malodour. Therefore, a suitable method is necessary for sediment disposition and NH₃-N removal in malodorous rivers. The sediment in a malodorous river (PS) in Beijing, China was selected and modified via calcination (PS-D), Na⁺ doping (PS-Na) and calcination-Na⁺ doping (PS-DNa). The NH₃-N removal efficiency using the four sediment materials was evaluated, and results indicated that the NH₃-N removal efficiency using the modified sediment materials could reach over 60%. PS-DNa achieved the highest NH₃-N removal efficiency (90.04%). The kinetics study showed that the pseudo-second-order model could effectively describe the sorption kinetics and that the exterior activated site had the main function of P sorption. The results of the sorption isotherms indicated that the maximum sorption capacities of PS-Na, PS-D and PS-DNa were 0.343, 0.831 and 1.113 mg g^-1, respectively, and a high temperature was favourable to sorption. The calculated thermodynamic parameters suggested that sorption was a feasible or spontaneous (ΔG < 0), entropy-driven (ΔS > 0), and endothermic (ΔH > 0) reaction.